Air curtain



FIG. 1 is a perspective view of an air curtain showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a rear elevational view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is an end view thereof as seen from the upper right side of FIG.1, the view of the other end of the air curtain being a mirror imagethereof.

The ornamental design for an air curtain, as shown and described.